Safety device



- Oct. 20, 1931 w. E. BRINDLEY SAFETY DEVICE Filed Feb. 4. 192a I INVENTOR M/fiam 5 B/T/Dd/Qy Y B I 7 A'II'TORNEY Patented Oct. 20, 1931 WILLIAM E. BRINDLEY, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T0 WESTING- HOUSE ELECTRIC & NUFACTUBING COMPANY, A CORPORATION OF IENNSYIP sararr nnvrcn Application filed- Eebruary e, was. Serial at. 251,901.

instead of so-called A and B battery eliminator's which derive unipotential currents from any convenient alternating-Current supply source. In some instances the A. and B eliminators are included within the cabinet of the receivingset proper, and the field winding of a separately housed electrodynamic loud speaker has been utilized as a constituent part of the filter circuits necessarily included in the said battery substitutes. For convenience in handling-and shipping, the loud speaker has usually been separabiiy connected to the receivin set by a plug-an socket device so dispose? cessible.

Receiving sets of the type described have, in general, given a fair de es of satisfaction. At the same time, the elimination of the alternating-current hum has not been entirely complete, thermionic-tube failures have been unduly fre uent, and the by-pass condensers comprised in the filter circuits often broke down from causesnthat were obscure.

It is, accordingly, one object of my invention to provide a current-distribution system for thermionic devices that shall be substantially free from objectionable disturbances.

Another object of my invention is to provide a current-distribution system for thermionic devices that shall be conducive to long tube-life.

Another object of my invention is to pro- I vide a radio receivin system, and a batterysubstitute therefor, t e combined apparatus incorporating protective devices for preventing" failure of the filter elements included in the said battery substitute. I

Another object ofmy invention is to provide a radio receiving system, and a batteryed current to a load in substitute therefor, the combined apparatus incorporating devices for preventing injury to the thermlonic tubes when a reactive element is removed from the saidbattery substitute during such time as the set is inoperation.

In one specific commercial embodiment of my invention, I accomplish the aforementioned objects by connecting the filaments of a plurality of thermionic devices in series across a minor portion of the output resistor of a rectifier-filter assembly andby connecting a potential-stabilizing device of the gaseous type across the entire output resistor. In addition, I associate a circuit-reestablishing device, with the plug-and-socket elements utilized to connect the field winding of a separately housed loud speaker into the filtercircuit, in order that unduly high voltages shall not be a plied to the condensers comprised in the 'lter-circuit, and in order that the potential supply to the several thermionic devices shall not'be interrupted, when the loud-speaker winding is removed from the as to be easily accircuit. I i

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with further objects and advantages thereof, will best be understood by reference to the following description of a specific embodiment, taken in connection with the accompanying drawings.- I

Fig. l of the drawings is a diagrammatic view of the circuits and apparatus involved in radio receiving apparatus comprising preferred embodiment of my invention.

Fig. 2 is a View, partly in section, of the plug-and-socket elements utilized for removably connecting an inductor into the filter circuit.

The apparatus illustrated in the drawings convenient source 3 of alternating current. i The high-potentialeoutput terminals of the rectifier-are connected to a resistor 4 by means of a conductor 5 and through a plurality of iron core inductors 6 and 7, the inductor 7 constitutin the field winding of a soundproducing evice 8. The low potential end I v of the resistor 4 has a ground connection 9.

A plurality of by-pass condensers 10, 11, 12, 13, 14 and 15 are connected in shunt to the rectifierv terminals, and in shunt to the resistor, for the purpose of absorbing potential fluctuations across the said output.

The field winding of the loud speaker 8 is connected into the filter circuit by means of i a plug-and-socket device 16, which device is illustrated in detail in Fig. 2. r The device 16 comprises a casin element 17 which insulatingly carries a p urality. of terminals 18 and'20, these terminals being connected respectively to the output circuit of the rectifier and to the negative terminal of the resistor 4. The member 16 also carries a resilient contact device 21 which may be permanently connected direct to ground, or be connected thereto through a resistor 22. The contact device- 21 is so disposed as to make contact with the terminal 18 when the plug is removed from the socket. The purpose of this grounding device will be later explained morein detail.

A plurality 'of thermionic devices 23, 24, 25, 26 and 27, having grids, filaments and anodes, are arranged with their filaments connected in series around a minor ortion 28 of the negative end of the resistor 4. Each filament has a resistor 30 connected in shunt thereto, the magnitudes of the several resistors decreasing progressively toward the grounded end of the resistor 4.

Anode potential for the thermionic devices 23, 25, 26 and 27 is derived from a point 31 on the resistor 4 which is adjacent to the upper or, ositive end thereof.

An e potential for the thermionic device 24, which functions as a detector, is obtained from. a point 32 on the resistor having a less p 1 1sitli1ve potential than the point 31 from w 10 audio-frequency transformer 33 is connected in the anode supply circuit of the thermionic device 23, one terminal of the secondary winding of this transformer being connected to the def a wer-amplifyin device 34. The fila dient of the thermionic evice 34. is energized from a second winding 35 of he other terminal of the transformer secondaryis' connected, through a resistor 36, to the midpoint .of a resistor 37 which is connected in shunt to the filament of the power amplifier.

A telephone jack 38 isiincluded in the circuit associated with the primary winding of. .the transformer 33, in order that a pair of telephones (not shown) may be utilized for signal reception of the loud speaker 8.

Anode. potential for the power amplifier tube 34 is derived from the most positive end of the resistor 4, the circuit therefor being:

tential for the remaining tubes is obt'aine The primary winding of an traced from the resistor, through the primary of an outputtransformer 40,'to the anode. The secondary of the power transformer 40 is connected to a movable coil 41 carried by the diaphragm of the loud speaker 8, which coil lies in an air-gap in a magnetic circuit energized from the field winding 7.

g In order that the grids of the several tubes shall be maintained at the proper biasing potentials, the grid-return conductors therefrom are connected to points in the filament supply circuit which are, in general, more negative than the filaments with which the said grids are respectively associated.

otential-stabilizing device 42 is connecte between the point 31 on the resistor 4 from which anode potential for the thermionic devices 23, 25, 26 and 27 is obtained and the lower, or grounded, end of the said resistor.

The voltage-stabilizing device 42, in a preferred embodiment of my invention, comprises a vitreous container, which may be of glass, having a plurality of coaxial electrodes 43 and 44 mounted therein. The electrode 43 is preferably cylindrical in form and encircles the electrode 44, which may well be a single straight wire. The envelope contains a gas at low pressure, the gas being preferably of such nature that it does not attack the electrode-materials. Devices of this character are well known inthe art and have the characteristic of maintaining the potential drop across their electrodes substantially constant, even though the current therethrough varies materially.

In a preferred embodiment of my invention, the total potential impressed across the resistor 4 by the rectifying device is 530 volts, the potentlal dro across the minor portion utilized for supp ying the filaments of the tubes being preferably of the order of 30 volts.

The resistor 36 in the grid circuit of the power-amplifier tube is preferably. so chosen that the space current in the said tube, when flowing at its normal value, causes a; drothereacross' of 80 volts, which is amply su cient to properly bias the grid of the device.

The thermionic devices 23, 24, 25, 26 and 1 27 are preferably of the type commercially known as UK 199, which have a filament current consumption of .06 amperes, with a; voltage drop of 3 volts In order, therefore, to utilize the entire 30 volts drop across the mmor portion of the resistor, an additional resistor 45 is included in the filament sup ly circuit, the magnitude of this resistor being so chosen that te'voltage drop across it is the same as that across the several tubes and their.

associated resistors.

Small changes in the potential applied froin the rectlfier across the resistor 4 are largely absorbed"'by the voltage-stabilizing device 42 and they, accordingly, give rise to extremely small changes across the minor portion 28 of the said resistor. Furthermore, since the filaments are connected in series across the said minor portion, each filament is subjected to only a fractional part of the entire voltage change across such portion.

The field winding 7 of the loud speaker, when connectedinto the filter circuit by means of the plug and socket device 16, carrles a current of 100 milliamperes. If the plug should be abruptly removed from the socket,

-ei her intentionally or accidentally, when the set is in operation, an abnormal potential would be applied across the filter condensers 10 and 11, were it not for the presence of the circuit-reestablishing contact 21 and the resistor 22. If these latter elements are omitted, as they were in certain prior-art devices with which I am familiar, the potential applied to the by-pass condensers was, in many instances, sufiicient to rupture the insulation thereof. The resistor 22, if present, is prefably so chosen that it has a ma nitude approximately the same as the inductive reactance of the field winding, in order that the removal of the said field winding shall cause only a slight change in the potential ap lied across the resistor l. Such being the ase, there is substantially no change in the filament treating current of the several thermionic devices when the loud-speaker winding is removed from circuit, and there is no marked change in the plate potentials applied thereto. This state of aflairs is conducive to longer tube life since, as is well known to those skilled in the art, thoriatedfilament tubes deteriorate rapidly if the said filaments are subjected to temperatures different from their normal operating temperature.

The grounding device associated with the socket in which the conductors from the loud speaker are inserted, serves also to protect the operator against shock when the plug is either inserted or removed. It will thus be apparent to those skilled in the art that I have provided, by my invention, a combined radio receiving set and battery eliminator that has numerous novel features. The plug-in arrangement, whereby the field winding of a separately housed loudspeaker may be utilized in the filter-circuit portion of the device, is a convenience, both in the operation of the set and in its shipment. The circuit-reestablishing means associated with the socket prevents abnortime, obviates the necessity of manually closing the said circuit to effect operation of the receiving set after the loud speaker has been removed. i

' The resistor 4 may,of course, be replaced by an inductive reactor, if it is desired. to

make frequent use of the receiving set with telephones instead of with a loud speaker.

By connecting the filaments of the thermionic devices serially across a resistor which is protected against potential changes by a gaseous conduction device, I am enabled to maintain the filaments at substantially a constant temperature, thus insuring good signal quality and, at the same time, preventing the said filaments from deteriorating rapidly.

Although I have illustrated and described only one specific embodiment of my invention, many other modificationsthereof will be apparent to those skilledin the art. My invention, therefore, is not to be limited, ex-w cept insofar as is necessitated by the prior art or by the spirit of the appended claims.

I claim as my invention:

1. In combination, a source of unidirectional fluctuating current, a filter comprising a plurality of inductors and a capacitor for sensibly lessening said fluctuations, one of said inductors serving also as the field coil of a sound producing apparatus, means for disconnecting said field coil from said filter, and means for preventing the building up of abnormal potentials on said capacitor, upon the disconnection of said field coil.

2. In combination, a source of unidirectional fluctuating current, a filter comprising a plurality of inductors and a capacitor tor sensibly lessening said fluctuations, one of said inductors serving also as the field coil of a sound producing device and being removable at will from said filter, and means including a grounding device and a resistor for preventing the building up of abnormal potentials'on said capacitor upon the disconnection of said inductor.

3. In a current distribution system, a source of fluctuating potential, a resistor connected across said source, a potential-stabilizing device connected across a portion of said resistor, and a load connected across a minor'portion of said resistor, said load in- W?) eluding a plurality of similar units in series, whereby any change in the potential across the whole of said resistor will produce little change across said minor portion and only a small fraction of said change will occur n across any one of said units. 7

4. In combination, a source of unidirectional fluctuating current, a filter comprising a reactor and a capacitor for sensibly lessening said fluctuations, means for removing 1% said reactor from said filter and means for preventing abnormal potentials from building up across said filter when said reactor is removed from tile circuit. i

5. In combination, a source of unidirectional fluctuating current, a filter comprising a reactor and a capacitor for sensibly lessening said fluctuations, sound-producing means having a winding whichis constituted by said reactor, a plurality of thermionic de vices associated with said filter, means for disconnecting said reactor from said filter circuit, meansfor preventing abnormal potentials from being applied across said filter upon the disconnecting of said reactor, said means also serving to prevent the-dissociation of said thermionic devices from said filter.

' 6. In combination, a source of high-potem tial fluctuating current, a resistor shunting said source, a plurality of thermionic devices associated wi h said resistor for deriving to said plates and filaments.

both plate and filament excitation therefrom, andwmeans comprising a voltage-regulating device for stabihzingthe excitation supplied 7. In a current-distribution system, a sourceof fluctuating potential, a resistor connected across said source, potential-stabilizing means connected across a portion of said resistor, a load comprisingthe filaments of a plurality of thermionic devices connected across a portion of said resistor included in the portion thereof'across' which said stabilizing means is-connected, the plate excitation for said thermionic devices also being obtained fromzsaid portion of said resistor I across which said stabilizing means is connected.

In testimony whereof, I have hereunto subscribed my namg this first day of February,-

' WILLIAM E. BRINDLEY. 

